Method for inducing twin calving

ABSTRACT

The present invention provides a method for inducing twin calving. The method according to the present invention comprises firstly treatment to inducing atresia of the antral follicles on ovary so as to initiate the development of new follicular wave, inducing the development of codominant follicles and further achieving double ovulations by exactly controlling the dosage and time points of hormone injections, and performing artificial insemination to induce the cow to deliver twin calves. The method according to the present invention has relative independent on the technical skills, and a person skilled in the art or a common worker can practice it according to specified operation methods; and during practical application, it does not require special equipment, thus saving cost, as well as improving the social benefit and economic benefit of cow breeding.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(a)-(d) to ChineseApplication No. CN201310195475.6, filed May 23, 2013, which is hereinincorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to the field of livestock reproduction,particularly to a method for inducing twin calving.

BACKGROUND ART

Cattle are monovular and produce only one calf per year in the naturalstate. For improving the reproductive efficiency of cow, effects havebeen conducted to control the number of dominant follicles in the ovaryby using various methods, and induce to form codominant follicles andthen ovulate two follicles, thereby achieving the purpose of producingtwo calves.

Currently, several methods are frequently used to induce a cow toproduce two calves, which were showed as follow: (1) Hormone inductionmethod: using hormones such as PMSG or FSH (TAN Niannian, 2000; WANGZhengchen, 2004) to induce a cow to produce two calves throughearly-stage small-dosage treatment, however, the half-life of PMSG islong, and thus the development of follicles would be disturbedconsistently, therefore the stability and feasibility of this method ispoor; further, with respect to the method by treatment with FSH alone,the number of codominant follicles cannot be easily controlled,therefore it is not feasible and convenient for practical application.(2) Mechanical aspiration method: aspirating all of the follicles >4 mm4-6 days after ovulation by virtue of a B ultrasound machine (Acosta etal., 2005; Palhao et al., 2009) so as to make the concentration of FSHdecrease to the lowest level on the day of aspiration (Kulick et al.,2001), thereafter, the elevation of FSH and the emergence of newfollicular wave are just synchronous, thus increasing the probability ofproducing codominant follicles. (3) Hormone plus mechanical aspirationmethod: a study (G. Glick et al., 2013) has used small doses of FSH toinduce double ovulations of a cow. Although 2-3 ovulations can beachieved at the rate of 90%, the procedure thereof comprises usingspecial estrus synchronization treatment 13 days before the experiment,and aspirating more than 3 large follicles via vaginal wall by using a Bultrasound machine on day 7 of the experiment, so as to achieve thepurpose of 2-3 ovulations. Therefore, it is difficult to popularize inthe production due to high technical operation and expensive instrumentsrequired by follicle aspiration. (4) Inhibitor immunization: somestudies used inhibin (gene) immunization (YANG Liguo, 2002; WANGShuilian, 2009) to adjust the endogenous secretion of FSH, and achievedsome effects, but the extraction and the purification of inhibin and thepreparation of gene vaccine are complex, and commercial drugs are notcommercialized yet, thus it is not popularized in the practice.

All above these methods have defects such as poor stabilization ordifficult operational technology, and are difficult to be generalizedand applied practically. Hence, there is a need to develop a simple andpractical method for inducing twin calving in the field application.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for inducinga cow to deliver twin calves, so as to overcome the disadvantages of thepresent method, which is largely dependent on the technical skill andneed a high cost of devices.

For achieving the above object, a method for inducing twin calvingaccording to the present invention comprises following steps:

1) on day 0 of the treatment, inserting an intravaginal progesteronereleasing device in a cow and injecting progestin and estrogen to causethe atresia of antral follicle and initiate a new follicular wave;

2) on day 4.5-6, injecting follicle-stimulating hormone (FSH) for 4times at 10-14 h intervals with sequential injection dosages of 5.5-6.5U/cow, 5.5-6.5 U/cow, 4.5-5.5 U/cow and 4.5-5.5 U/cow, leading to thedevelopment of codominant follicle in the new follicular wave;

3) on day 6.5-7.5, injecting estrogen to inhibit the secretion of FSHthrough a negative feedback, so as to inhibit further development ofsmall follicles that have not been dominant;

4) on day 8, removing the intravaginal progesterone releasing device andinjecting estrogen to induce large follicle ovulate;

5) on day 9.5-10, performing artificial insemination (AI).

In the step 1), the injection dosages of the progestin and the estrogenare 45-55 mg/cow and 3.5-4.5 mg/cow respectively, preferably 50 mg/cowand 4 mg/cow;

In the step 2), preferably, on day 4.5-6, FSH is injected in 4 times at12 h intervals with sequential injection dosages of 6 U/cow, 6 U/cow, 5U/cow and 5 U/cow;

In the step 3), on day 6.5-7.5, the estrogen is injected in 3 times at10-14 h intervals with each injection dosage of 0.15-0.25 mg/cow, andprostaglandin (PG) is additionally injected with each dosage of 20-30mg/cow in the last 2 times respectively. Preferably, the estrogen isinjected in 3 times at 12 h intervals with each injection dosage of 0.2mg/cow, and PG is additionally injected with each dosage of 25 mg/cow inthe last 2 times respectively;

In the step 4), on day 8, the intravaginal progesterone releasing deviceis removed, and the estrogen is injected at dosage of 1-2 mg/cow,preferably 1.5 mg/cow;

In the step 5), preferably, on day 9.5-10, AI is performed twice, and 2mg of luteinizing hormone (LH) is injected at the first AI.

The estrogen comprises, but not limited to, estradiol benzoate (EB) orestradiol valerate (EV) injection, preferably EB.

The progestin includes, but not limited to, progesterone (P₄) ormedroxyprogesteroneacetate (MPA), preferably P₄.

A preferable method in Examples of the present invention comprises: onday 0, inserting an intravaginal progesterone releasing device (CIDR),and injecting 4 mg of EB and 50 mg of P₄; on day 4.5-6, injecting FSH in4 times at 12 h intervals with dosages of 6 U/cow, 6 U/cow, 5 U/cow and5 U/cow; on day 6.5-7.5, injecting EB in 3 times at 12 h intervals witha dosage of 0.2 mg/cow·time, wherein PG (lutalyse) is additionallyinjected with a dosage of 25 mg/cow·time in last 2 times respectively ;on day 8, removing the CIDR, and injecting 1.5 mg of EB; and on day 9.5and day 10, performing AI twice, and injecting 2 mg of LH in the firstAI.

The invention, based on the dynamics and functional characteristics ofinvolved hormones during follicle genesis under cow physiologicalstatus, combines several hormones in early-stage treatment to reset newfollicular wave, and apply appropriate amount of FSH to the cow beforefollicle deviation by accurately controlling the treatment time ofrelevant hormones, so as to induce codominant follicles; small-dosageestrogen is applied and inhibits the secretion of cow endogenous FSHthrough negative-feedback, so that the development of non-dominantfollicles was inhibited, and the codominant follicles whose developmenthas been initiated continues to develop to ovulation stage for notcompletely depending on FSH during later stage of recruitment. Comparedwith the conventional methods by using FSH or PMSG alone, the presentmethod can control the development of a small number of follicles (2-3)to deviation stage through deviated small-dosage estrogen treatment, andfurther achieve the purpose of producing two calves.

In the step 1) of the present invention, a CIDR is inserted into a cow,and progestin and estrogen are injected. It is expected that after 12 h,the concentrations of FSH and LH in cow body will decrease to the lowestlevel, so that the development of antral follicles in ovary areinhibited, atresia occurs about 36 h after inserting the CIDR, and newfollicular wave startup 4 days later.

In the step 2) of the present invention, the small doses of FSH isinjected before follicle deviation so as to induce the development ofcodominant follicles; and in the step 3), after startup of codominantfollicles, the estrogen is injected to inhibit the secretion of FSH bynegative feedback, so that the development of non-dominant follicles isinhibited, so as to ensure that the number of dominant follicles is notincreased.

The steps 4) and 5) of the present invention realizes the ovulation ofdominant follicles, and achieves twin calving production throughartificial insemination.

The method according to the present invention has a lower dependency ontechnical skill, and may be practiced by a person skilled in this fieldor a common worker according to specified operation methods; inaddition, this method does not require special equipment, thus ensuringoperation feasibility under large-scale production condition.

For a long time, the low reproductive rate of cow results in highfeeding cost and low economic benefit. However, the method based on thepresent invention can induce a cow to double ovulate and deliver twincalves. On one hand, it can rapidly propagate productive group, increasemilk yield or meat yield and further improve breeding benefit; on theother hand, it can reduce the feed amount of cow by improving theutilization efficiency of cow, and therefore effectively control thecost of feeding and management and thereby alleviate the environmentalpollution caused by largely breeding of cow.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is the flow diagram of the method according to the presentinvention.

EXAMPLES

Following examples are used for further illustrating the presentinvention, but should not be understood to limit the present invention.All modifications or equivalent replacements to the present inventionwithout departing from the spirit and the substance of the presentinvention are covered in the scopes of the appended Claims.

Example 1

According to the flow diagram shown in FIG. 1, 15-18-month-aged cows (30of Simmental beef cows and 30 of Holstein dairy cows) are treated. Onday 0 of the treatment, a CIDR (US Pfizer, USA) is inserted into thecows, and 4 mg of EB (Ningbo SANSHENG, China) and 50 mg of P₄ (NingboSANSHENG, China) are injected; on day 4.5-6, FSH (SIOUX, USA) isinjected 4 times at 12 h intervals with dosages of 6 U/cow, 6 U/cow, 5U/cow and 5 U/cow; on day 6.5-7.5, EB (Ningbo SANSHENG, China) isinjected in 3 times at 12 h intervals with dosage of 0.2 mg/cow·time,wherein PG (lutalyse, US Pfizer, USA) is additionally injected in last 2times respectively with dosage of 25 mg/cow·time; on day 8, the CIDR isremoved, and 1.5 mg of EB is injected; and on day 9.5 and day 10, AI isperformed twice, and 2 mg of LH (Ningbo SANSHENG, China) is injected inthe first AI.

The results show that: according to the present invention, afterartificial insemination, first-cycle conception rate is 80%, calvingrate (calving cow/inseminated cow) is 78%, and two-calf rate (cowsdelivering twin-calves cow/calving cows) is 62.5%, while afterconventional artificial insemination, first-cycle conception rate is60%, and calving rate is 55%. Thus, the present invention cansignificantly improve the reproductive efficiency of cow, and achieve asatisfying effect both in beef and dairy cow.

The various embodiments described above are provided by way ofillustration only and should not be construed to limit the claimedinvention. Those skilled in the art will readily recognize variousmodifications and changes that may be made to the claimed inventionwithout following the example embodiments and applications illustratedand described herein, and without departing from the true spirit andscope of the claimed invention, which is set forth in the followingclaims.

What is claimed is:
 1. A method for inducing a cow to produce twocalves, comprising: on day 0 of the treatment, inserting an intravaginalprogesterone releasing device into a cow and injecting progestin andestrogen so as to cause the follicular atresia and initiate thedevelopment of new follicular wave; on day 4.5-6, injectingfollicle-stimulating hormone (FSH) in 4 times at 10-14 h intervals withsequential injection dosages of 5.5-6.5 U/cow, 5.5-6.5 U/cow, 4.5-5.5U/cow and 4.5-5.5 U/cow, leading to the development of codominantfollicle in the new follicular wave; on day 6.5-7.5, injecting estrogento inhibit the secretion of FSH through a negative feedback, so as toinhibit non-dominant follicles from further developing; on day 8,removing the intravaginal progesterone releasing device and injectingestrogen to induce dominant follicle ovulate; on day 9.5-10, performingartificial insemination (AI).
 2. The method according to claim 1,wherein in the step 1), the injection dosages of progestin and estrogenare 45-55 mg/cow and 3.5-4.5 mg/cow respectively.
 3. The methodaccording to claim 2, wherein in the step 1), the injection dosages ofprogestin and estrogen are 50 mg/cow and 4 mg/cow respectively.
 4. Themethod according to claim 1, wherein in the step 2), on day 4.5-6, FSHis injected in 4 times at 12 h intervals with sequential injectiondosages of 6 U/cow, 6 U/cow, 5 U/cow and 5 U/cow.
 5. The methodaccording to any one of claims 1-4, wherein in the step 3), on day6.5-7.5, the estrogen is injected in 3 times at 10-14 h intervals witheach injection dosage of 0.15-0.25 mg/cow, and prostaglandin (PG) isadditionally injected with each dosage of 20-30 mg/cow in the last 2times respectively.
 6. The method according to claim 5, wherein in thestep 3), on day 6.5-7.5, the estrogen is injected in 3 times at 12 hintervals with each injection dosage of 0.2 mg/cow, and prostaglandin isadditionally injected with each dosage of 25 mg/cow in the last 2 timesrespectively.
 7. The method according to any one of claims 1-4, whereinin the step 4), on day 8, the intravaginal progesterone releasing deviceis removed, and the estrogen is injected with dosages of 1-2 mg/cow. 8.The method according to any one of claims 1-4, wherein in the step 5),preferably on day 9.5 and day 10, artificial insemination is performedtwice, and luteinizing hormone (LH) is injected with dosages of 2 mg/cowin the first artificial insemination.
 9. The method according to any oneof claims 1-4, wherein the estrogen is estradiol benzoate (EB).
 10. Themethod according to any one of claims 1-4, wherein the progestin isprogesterone (P₄).